It just feels unintuitive. Weaving it into normal gameplay with only procs feels like a wasted talent point. Why wait for procs to be able to use mind spike if they could just increase the reset chance of mind blast? It also makes shadow very busy and cluttered with high haste levels.
A fully dotless playstyle with mindspike as your filler on the other hand also isn't supported since you basically waste half your talent points you have to spend on dot damage anyway and you want to use your insanity for plague. Dark ascension even generates a lot which makes capping and overgenerating insanity even more likely during that window.
It just needs a lot of finetuning to feel right for me personally. Maybe if it doesn't clear plague is enough to do so. Or maybe im just dissapointed because i hoped they would nail the flow of wod priest.